Proximity monitoring systems for persons or objects have been provided which comprise a transmitter and receiver for position reporting. These systems have deficiencies in an inability to process a plurality of signals from multiple units in a limited area, particularly in a short time span. With substantially simultaneous multiple transmissions to a common receiver collisions occur which hinder or defeat the desired identification of the transmitters.
The actuating means which trigger the transmission of identifying signals from these transmitters are operated by means which are occasional in nature. For example, various previous systems which transmit a coded RF signal are actuated by a mechanical-type of operation, such as a switch actuated by a coded card or detection unit such as a peripheral instrusion detector. These triggering means fail to provide a continuous, and regularly present triggering means which is also variable.
It is an object of this invention to provide a system for variably controlling the initiation of a periodic pulse cyclically produced.
More particularly, it is an object to provide for varying the timing of the actuation of sequencing of addresses in a memory into which information can be introduced and later extracted.
Specifically, it is an object to provide a simple transmitter carried by each individual, which issues a characteristic and coded identifying signal upon regularly periodic actuation, so that transmission and identification of a plurality of distinctively characteristic signals within a system of transistors is accomplished by varying the timing of the various periodic transmissions to avoid collisions between receptions at a common receiver.